Current requirements for private aircraft landing: I am planning a trip in a private airplane, a Piper Cherokee 180 four seat airplane with a total of four of us flying in. What are the current requiremts? Do you know if I can stop in Mexico to refue

You will need Mexican insurance, through a Mexican agent, AOPA has information on providers. You will most likely have to pay a landing fee. Also, when you head north, you must stop first in Cozumel or Topachula on the Pacific to clear into Mexico (only airports of entry for north bound private aircraft.), that is where you may end up paying an unreasonable amount.